This invention relates to sharpening device, and more particularly to a sharpening device for an elongated object with non-circular cross section, such as a carpenter""s pencil.
Most pencil sharpening devices currently in use are designed for making round tapered points on pencils having cross-sections, which are either circular or in the shape of a regular polygon, generally hexagonal. This typical geometry, such as round or hexagonal, is not compatible with the rectangular lead pencils used by many professionals, including the well-known carpenter""s pencil. It is desirable that carpenter""s pencils be sharpened to create a selected profile rather than a point. The wooden sheath around the pencil lead is also non-circular, e.g., rectangular, with narrow edges and wide edges oriented at right angles to one another.
Existing pencil sharpening devices which are suitable for circular or hexagonal cross-sections are usually constructed to require a rotational movement of blades around the axis of the pencil being sharpened. This type of mechanical action will not create the desired profile for a carpenter""s pencil. As a consequence, the user is reduced to manually shaving or scrapping the carpenter""s pencil to provide the desired profile.
A number of authors have suggested sharpening devices especially designed for pencils of rectangular or non-circular cross-sections. These are listed as follows:
The foregoing devices generally require rotary cutter assemblies which are mounted or manipulated so as to accommodate the irregular cross-section of the carpenter""s pencil. They involve complicated and expensive mechanisms.
A commercial pencil sharpener for a carpenter""s pencil is manufactured by Penshar LLC, which is manually rotated. However, this sharpener puts a conical end on the carpenter""s pencil.
It would be desirable to have a sharpening device which will sharpen or shape wooden or similar non-metallic elongated objects having radially non-symmetrical cross-sections. It would also be desirable to have a low cost sharpening device especially adapted to sharpen a carpenter""s pencil and provide a selected profile. It would also be desirable to have a low cost manually operated sharpening device for carpenter""s pencils.
Accordingly, one object of the present invention is to provide a low cost sharpening or carpenter""s pencils.
Another object of the invention is to provide a sharpening device for lead pencils of non-circular cross-sections or similar elongated objects which will sharpen or shape one end of the object to a desired profile.
Briefly stated the invention comprises apparatus for sharpening an elongated object so as to obtain a selected projected profile on one end of the elongated object, the elongated object having a uniform cross section along an object axis. The apparatus comprises a housing defining a recess having an opening and having a pair of convergent walls within the recess, a guide member slidably mounted on the housing on guide rails, the guide member defining a passage therethrough. The passage is shaped and dimensioned to receive the elongated object and to guide the object for longitudinal motion along the object axis between the convergent walls when manually actuated by a user, and at least one blade having a cutting edge and disposed on at least one of the opposed walls with the cutting edge extending into the recess, whereby the elongated object may be pushed through the passage of the guide toward the convergent walls while the elongated object is also being used to slide the guide member to move the end of the elongated object laterally back and forth past the cutting edges of the blades, so as to sharpen the elongated object to obtain the selected profile.
Preferably the apparatus is designed to sharpen a carpenter""s pencil, and includes a duplicate set of recesses, convergent walls, guide members, and blades, one set accommodating the carpenter""s pencil in one rotated position about its axis to shape the wide side, and the other set accommodating the carpenter""s pencil in a different rotated position about its axis to shape the narrow side.